1. Field of the Invention
The present invention relates to a vacuum pump suitable for exhaust of a gas that easily causes product deposition.
2. Description of the Related Art
Conventionally, a vacuum pump such as a turbo-molecular pump and the like has been used for chamber exhaust of a semiconductor manufacturing device, a liquid crystal manufacturing device or the like. In recent years, troubles have increased that in an etching process of a semiconductor manufacturing device and a liquid crystal manufacturing device, deposition of products on a vacuum pump is caused, so that a rotor of the vacuum pomp comes into contact with the products, and a problem or the like has arisen that an overhaul is required in a short period after the device starts operating.
These products are also deposited on an exhaust duct provided in a gas exhaust section of the vacuum pump. Since a pressure inside the exhaust duct is higher than that inside the vacuum pump, the product deposition in the exhaust duct is remarkable. When the product deposition inside the exhaust duct becomes remarkable, a duct line becomes gradually blocked, and a pump back pressure rises, which brings about a decrease in pump performance. Moreover, an increase in load accompanying the rise in pump back pressure increases pump heat generation, which brings about a rise in rotating body temperature. As a result, there arises a problem that a creep life of the rotor is lowered.
As a technique for reducing the above-described deposition of the products, a constitution described in Patent Literature 1 (Japanese Unexamined Patent Application Publication No. H6-159287) has been known. In a turbo-molecular pump described in Patent Literature 1, in a gas flow channel inside the pump, a partition wall made of a heat transfer body is provided, and the partition wall and a heating section located outside the pump are joined by a good conductor of heat, and the heating section is heated by an electric heater or the like.
However, in the case where heating is performed by the electric heater or the like, a heater, a temperature sensor, a controller for controlling the heater and the like, and the like are required separately.